CVE-2026-89641

Kernel use-after-free via stale CIFS tcon reuse

Published Sep 11, 2026 · Updated Sep 11, 2026

Use-after-free in the Linux 6.18 CIFS client allows local users to dereference freed kernel memory during a failed file-size update. In cifs_file_set_size(), a failed handle-based set_file_size() releases the file handle but leaves its borrowed tcon non-null, so set_path_size() reuses freed memory. Reachability requires a writable CIFS handle, a failed size-change RPC, and reconnection or session teardown that removes the final tlink reference.

CVSS severityUnavailable
Unscored
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Linux 6.18 CIFS client allows local users to dereference freed kernel memory during a failed file-size update. In cifs_file_set_size(), a failed handle-based set_file_size() releases the file handle but leaves its borrowed tcon non-null, so set_path_size() reuses freed memory. Reachability requires a writable CIFS handle, a failed size-change RPC, and reconnection or session teardown that removes the final tlink reference.

The record

CVE
CVE-2026-89641
Published
Sep 11, 2026
Updated
Sep 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=110fee6b9bb58a5c50047fc2594d415f741b591e <4bea15d9c7683218f57b8c1f5f0aa75cab76af8d
  2. Affected versionversion=110fee6b9bb58a5c50047fc2594d415f741b591e <4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4
  3. Affected versionversion=110fee6b9bb58a5c50047fc2594d415f741b591e <b96db32fed8dfb2478d7c208f89bf383beed1535
  4. Affected versionversion=6.18

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=110fee6b9bb58a5c50047fc2594d415f741b591e <4bea15d9c7683218f57b8c1f5f0aa75cab76af8d; version=110fee6b9bb58a5c50047fc2594d415f741b591e <4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4; version=110fee6b9bb58a5c50047fc2594d415f741b591e <b96db32fed8dfb2478d7c208f89bf383beed1535; version=6.18

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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